无规共聚聚丙烯管材氧化诱导时间测试探究

以无规共聚聚丙烯（PP?R）管材为研究对象，采用差示扫描量热仪（DSC）测试了PP?R管材的氧化诱导时间（OIT），并研究了测试部位、样品直径、样品厚度以及取样方式等测试条件对OIT测试结果的影响。结果表明，从垂直管壁方向取芯层直径为6 mm、厚度为650 μm的试样进行测试时，OIT测试结果相对可靠。     

DSC测定PP熔点过程中实验条件的优化

为了优化出DSC测定聚丙烯(PP)熔点过程中的最佳实验条件,通过单因素试验研究了差示扫描量热(DSC)仪测试PP熔点过程中常见影响因素(升温次数、吹扫气流速、升温速率、试样质量)对实验结果的影响;采用正交试验分析了主要影响因素之间的主次大小并优化出最佳的测试条件。实验结果表明,测定PP的熔点只需第2次升温,继续增加升温次数对实验结果的影响不大。吹扫气流速、升温速率与试样质量3个主要因素对PP熔点的影响规律是一致的,吹扫气流速变大,升温速率变快,试样质量越大,测得的PP熔点均变大。正交试验发现,该3因素对实验结果的影响程度不同,升温速率对实验结果的影响最大,试样质量次之,吹扫气流速的影响相对较小。确定的最佳实验条件为:试样质量5 mg,升温速率5 K/min,吹扫气流速60 mL/min。     

后处理对半芳香透明聚酰胺力学性能的影响

采用固相后缩聚工艺制备了一系列不同熔体流动速率的半芳香透明聚酰胺（SATPA）,研究了材料的吸水性能和调湿、退火后处理对材料力学性能的影响。结果表明,固相后缩聚SATPA的吸水性能不随熔体流动速率的减小而变化,但外界条件对吸收速率有一定影响,水温越高,环境湿度越大,试样吸水速率越大,吸水前后试样尺寸基本不变。调湿处理后,试样性能提高不明显,断裂伸长率下降;退火处理后,试样的拉伸强度、断裂伸长率和缺口冲击强度均有所提高。     

聚丙烯材料收缩率影响因素研究

制备了聚丙烯(PP)和改性聚丙烯材料(PP+EPDM-TD10)不同厚度的大尺寸收缩率试样,利用熔体流动速率仪、示差扫描量热仪和大尺寸收缩率检具分别分析了材料结晶度、流动性、热存放条件及制件壁厚对材料成型收缩率的影响.结果表明:PP材料结晶度越高,纵向(MD)和横向(TD)的成型收缩率均越大.同一注塑工艺情况下,流动性...     

外界环境因素对热塑性橡塑共混开孔材料的影响Ⅱ橡塑共混开孔材料的蠕变行为

研究了退火温度和时间及退火后放置时间对橡塑开孔材料透水速率的影响。结果表明：开孔材料透水速率随退火温度的升高而下降，退火温度越高，下降的幅度越大；同一退火温度下，透水速率随退火后放置时间的增长而降低，放置时间越长下降的幅度越大；透水速率随退火时间的增长而下降，退火时间越长，下降幅度越大。     

脱醇型RTV-1硅橡胶试样预处理对可冷凝成分测定结果的影响探讨

探讨了脱醇型单组分室温硫化(RTV-1)硅橡胶的试样形状、试样厚度、硫化时间对可冷凝成分测定结果的影响。结果表明,试样形状(由同厚度试片裁切而成)对其可冷凝成分测试结果无明显影响;随着硫化时间的延长,可冷凝成分测试结果降低;随着试样厚度的增加,可冷凝成分测试结果明显下降。因此建议:未硫化的RTV-1硅橡胶可按标准规定每份取10 g检测;对于硫化后的固态RTV-1硅橡胶,则先制成2 mm厚试片,在标准条件下硫化7天后裁成直径(80±1)mm的圆形试样检测。     

搅拌对胶料脆性温度测定结果的影响

试验研究试样冷冻期间搅拌对脆性温度测定结果的影响。结果表明:在其他试验条件不变的情况下,搅拌使胶料的脆性温度测定结果升高,且搅拌的速度越快,温升幅度越大;在用单试样法测定胶料的脆性温度时,试样冷冻期间不应启动搅拌器。     

注气压力对微发泡聚丙烯PVT特征的影响

通过自主设计的压力-比容-温度(PVT)测试装置,以定压升温的方法测试容积的变化,对微发泡聚丙烯(PP)的PVT特性进行了测试,研究不同注气压力对微发泡PP的PVT特征影响。结果表明:随着温度的升高,微发泡PP比容呈现上升趋势;不同的注气压力对于微发泡PP的比容有着明显的影响,温度一定时,随着注气压力的升高,微发泡PP比容也逐渐增大;随着注汽压力的增大,微发泡PP的拉伸强度逐渐下降;注气压力越高,微发泡PP制品内部的泡孔密度越大,泡孔尺寸也越小。     

石榴籽抗氧剂对聚丙烯抗氧化性能的研究

以饮料厂加工废弃物中的石榴籽为原料,提取其抗氧化活性物质,作为聚丙烯(PP)的抗氧剂。试样经过室内热氧老化,并对老化前后试样进行微量混合流变、氧化诱导时间、差示扫描量热分析、力学性能测试、投射电镜等分析判断石榴籽抗氧剂(PSA)对PP试样抗氧化程度的影响。结果表明,PSA可使PP试样流变扭矩与氧化诱导时间增大,对PP有一定的抗氧化作用;差示扫描量热(DSC)分析可知,PSA的加入不会对PP热性能以及结晶能力产生影响;经室内热氧老化后,PSA可有效保持PP各项力学性能,PSA质量分数为0.5%时抗氧化效果最佳。     

不同条件对聚碳酸酯缺口冲击强度测试结果的影响

以纯聚碳酸酯(PC)、阻燃PC和阻燃增韧PC试样为研究对象,研究了ISO 7391–2,ASTM D256和ISO180三种标准测试的悬臂梁缺口冲击强度差异,同时探讨了缺口制作方式和退火处理(135℃,2h)对缺口冲击强度测试结果的影响。结果表明,不同PC试样采用ASTM D256标准测试的缺口冲击强度较ISO 7391–2稍高,而采用ISO 180标准测试的缺口冲击强度最低。偏光应力仪和扫描电子显微镜测试结果表明,由于ISO 180标准规定的试样厚度相对较大,试样产生了过大的残余应力,加之阻燃PC中阻燃剂与PC的相容性较差,进而导致采用ISO 180标准测试的阻燃PC缺口冲击强度测试数据极低。实际应用中尽量选用断裂行程短、试样厚度大的ISO 180标准对改性PC试样的缺口冲击强度进行测试,其更能体现材料的缺陷和实际韧性。采用机铣缺口测试的缺口冲击强度稍高,而采用模塑缺口测试的缺口冲击强度离散系数小,数据稳定性更好。退火处理虽可消除试样的内部应力,但会导致试样边缘位置应力集中更加明显,退火处理后各试样的缺口冲击强度测试数据均大幅度降低。     

Temperature dependence of the brittleness of cellulose fibers and of chemically modified cellulose fibers

The temperature dependence of the brittleness of cellulose fibers was studied by the breaking twist angle method. The selected fibers were purified ramie cells, the same cells after fibrous acetylation to form the triacetate, annealed acetylated ramie cells, and mercerized ramie cells. Water acts as a plasticizer to reduce the brittleness of ramie and of mercerized ramie cells but does not appear to affect the brittleness of ramie cells after acetylation. The brittleness of ramie cells is reduced by similar amounts by fibrous acetylation and by mercerization. The brittleness of acetylated ramie cells is increased by annealing, which induces additional crystallization in the cells. The brittleness of ramie and acetylated ramie before and after annealing varied as the test temperature was progressively increased in the range 100–200°C. The effect of temperature on the brittleness of the fibers is interpreted in terms of the relaxation transitions previously determined on the same types of fibers, and in terms of the supramolecular structure of the fibers.     

Effects of annealing on the hierarchical crystalline structures and mechanical properties of injection‐molded bars of high‐density polyethylene

The effect of annealing on the microstructural evolution and mechanical properties of high‐density polyethylene parts molded via gas‐assisted injection molding was investigated using scanning electron microscopy, differential scanning calorimetry, two‐dimensional wide‐angle X‐ray diffraction and tensile testing. The results indicated that a variety of annealing temperatures could induce considerable variations in the hierarchical structures, crystallinity, lamellar thickness and yield stress of the molded bars. According to these results, the annealing temperatures could be divided into three regions. In the low‐temperature region of annealing at 80 °C, the spatial variation of the superstructure developed along the thickness direction and mechanical properties of the annealed sample were mainly unchanged and similar to those of the original specimen. At 100 and 120 °C, the intermediate temperature region of annealing, the thickness of the crystals, degree of orientation and yield stress of annealed samples were greatly improved. Finally, at 127 °C, the degree of orientation decreased and yield stress slightly improved, an indication of the high‐temperature annealing region being characterized by increasing melting/recrystallization and causing relaxation of oriented molecular chains. A model is proposed to interpret the mechanism of the annealing treatment of the samples at various temperatures. © 2013 Society of Chemical Industry     

浮法玻璃退火过程中玻璃带内的温度场和应力松弛

本文建立了浮法玻璃退火过程中玻璃带内温度场的数值计算与制图方法，并得出了玻璃带厚度方向温度分布随时间的变化关系。本文还做了玻璃应力松弛试验，结果表明，采用RD2-3型改进应力松弛试验机是可靠的。     

红枣冻干预冻工艺优化研究

采用电阻法测量了红枣的共晶点温度,其值为-32℃。在实验室冻干机上分别进行了单因素和正交实验,研究了冻结速度、枣片厚度、冻结温度和冻结时间对红枣预冻结的影响情况,得到了红枣冻干过程的冻结工艺最优参数为：冻结速度-1.0℃/min,枣片厚度8 mm,冻结温度-38℃,冻结时间210 min。     

Influence of annealing treatment on the structure and properties of poly(4‐methyl‐1‐pentene)‐based films and membranes

The poly(4‐methyl‐1‐pentene) casting films were prepared by melt extrusion and annealed below the melting temperature. The effect of annealing conditions on the structure and properties of casting films and stretched membranes was discussed. In this work, a new peak around annealing temperature, as shown in melting curves, revealed the increase in thickness of lamellar structure. Annealing treatment led to improvements of amorphous thickness and crystal orientation. And the thickness of crystal phase correlated with the logarithm of annealing time. The increase in annealing temperature or time led to the improvements of the hard elasticity of samples. Additionally, the larger porosity of stretched membranes was observed as the annealing time and temperature increased. An optimum annealing condition to prepare microporous membranes was 30 min, 200 °C. This work also discussed the importance of annealing treatment in the preparation of microporous membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46491.     

The effect of temperature and annealing on the phase composition, molecular mobility and the thickness of domains in high-density polyethylene

Molecular mobility, the thickness of domains and the amount of rigid, semi-rigid, and soft fractions of high-density polyethylene (HDPE) were characterized as a function of temperature and annealing time using time- and frequency-domains proton solid-state NMR. These experiments established the temperature range for which the largest differences are observed in molecular mobility in crystalline phase, semi-rigid crystal-amorphous interface, and soft fraction of the amorphous phase allowing accurate determination of the phase composition and the thickness of these domains. The domain thickness, which was determined by NMR, is in good agreement to those measured by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) on the same sample. Changes in molecular mobility in the amorphous phase upon increasing temperature and annealing are discussed. It is shown that annealing is accompanied by structural reorganizations in the amorphous layer adjacent to the lamella surface causing a continuous shift of the interface towards the inner part of the amorphous regions and thus reducing the thickness of the amorphous layer. A recently introduced method was used for measuring the thickness of domains by a spin-diffusion NMR experiment with a double-quantum dipolar filter. The temperature dependence of the spin diffusivities is reported for the three phases of HDPE. For the first time results of spin-diffusion experiment performed by time-domain low-field NMR and frequency-domain high-field NMR are compared.     

Effect of composition and high-temperature annealing on the local deformation behavior of silicon oxycarbides

Silicon oxycarbides with varying compositions were investigated concerning their elastic and plastic properties. Additionally, the impact of thermal annealing on their elastic properties was assessed. Phase separation of SiOC seems to have no significant impact on Young’s modulus (high values of β-SiC compensate the low values of the vitreous silica matrix) and hardness. However, it leads to an increase in Poisson’s ratio, indicating an increase in the atomic packing density. The phase composition of SiOC significantly influences Young’s modulus, hardness, brittleness and strain-rate sensitivity: the amount of both β-SiC and segregated carbon governs Young’s modulus and hardness, whereas the fraction of free carbon determines brittleness and strain-rate sensitivity. Thermal annealing of SiOC glass-ceramics leads to an increase in Young’s modulus. However, the temperature sensitivity of Young’s modulus and Poisson’s ratio is not affected, indicating the glassy matrix being stable during thermal annealing. A slightly improved ordering of the segregated carbon and the β-SiC nanoparticles upon thermal annealing was observed. It is suggested that this is responsible for the increase in Young’s modulus.     

Relationship between brittleness and moisture loss of concrete exposed to high temperatures

The effect of moisture loss at high temperatures on the brittleness of concrete was investigated by conducting three-point bending tests on preheated notched beams. The relationships of moisture loss represented by mass loss with heating temperature and exposure time could be established. Higher heating temperature always led to higher mass loss and lower brittleness. Longer exposure time led to higher mass loss and lower brittleness, but this effect was more significant at the early exposure stage and became insignificant thereafter. When concrete is exposed to high temperatures, the brittleness is reduced. The evaporation of gel water was more closely related to the brittleness.     

TiO_2–ZnO复合薄膜的制备及光致双亲性能

采用溶胶-凝胶法制备了TiO2薄膜和ZnO掺杂的TiOr-ZnO复合薄膜.通过X射线衍射和原予力显微镜表征了样品的晶相、晶粒尺寸和形貌.以水(H2O)作为极性溶液参照物,苯(C6H6)作为非极性溶液参照物,研究了煅烧温度、煅烧时间、薄膜层数对薄膜光致双亲性的影响.结果表明:煅烧温度和煅烧时间的不同能够导致薄膜的晶粒粒径、晶型及薄膜表面的粗糙度发生变化.从页影响薄膜的双亲性能.当煅烧温度为550℃,煅烧时间 为2h,薄膜层数为3层时.TiO2由锐钛矿相向金红石转变,薄膜的双亲性最传.TiO2-ZnO复合薄膜的晶粒粒径约为25.2nm,薄膜表面粗糙度约1.815 nm,此时,亲水角和亲油角分别为5°和4°.ZnO掺杂的TiO2复合薄膜的双亲性明显高于纯TiO2薄膜.     

热处理条件对聚丙烯流延基膜取向片晶结构及拉伸成孔性的影响

摘要：为了优化挤出流延单向拉伸法制备聚丙烯微孔膜的工艺,以温度、时间和基膜受到的张应力做为热处理条件变量,通过DSC、FTIR、SEM、电子材料试验机和透气率测试仪等方法表征流延基膜的取向片晶结构参数和微孔膜的孔结构,考察热处理条件对聚丙烯流延基膜取向片晶结构和拉伸成孔性的影响。研究表明,随热处理温度从120℃提高到145℃,基膜的取向片晶结构得到改善,硬弹性增强,拉伸成孔性能变好;随热处理时间延长,基膜的结晶度、片晶厚度及取向程度不断提高,取向片晶结构趋于完善,当热处理时间达到30min后,取向片晶结构的完善程度接近稳定;在热处理过程中对基膜施加适当张应力可以提高基膜的片晶取向程度和硬弹性,改善其拉伸成孔性。